Here's a reason Wait() should be allowed to be a configurable item. Let's say the inbound call flow would start by playing an announcement which then proceeds to an IVR with its announcement. The current Wait(1) is a sufficient time delay which causes what is heard to the caller to not sound as if a person was speaking to them.
Since tm1000 says by setting the immutable flag on extensions_additional.conf is sufficient reason to not use FreePBX, I ask then, when does the content of extensions_additional.conf change other than using the GUI to add/remote extensions/routes/trunks etc?